Hydraulic shock eliminator



9 1954 c. E. ADAMS 2'690762 HYDRAULIC SHOCK ELIMINATOR Filed June 23,1949 2 Sh ets-Sheet l IN VLN TOR. I CECIL E.ADAMS A T'I'ORNE Y.

Oct. 5, 1954 c. E. ADAMS 2,690,762

HYDRAULIC SHOCK ELIMINATOR Filed June 23, 1949 2 Sheets-Sheet 2 FIG-.6.

INVENTOR. CECIL E..ADAMS BY $416M M W Patented Oct. 5, 1954 UNITEDSTATES PATENT OFFICE Denison Engineering Company,

Columbus,

Ohio, a corporation of Ohio Application June 23, 1949, Serial No.100,790

Claims.

This invention relates generally to hydraulic apparatus and isparticularly directed to a mechanism which may be positioned in ahydraulic system to decrease or eliminate surge due to the introductionof high pressure fluid into a line or other part of a hydraulic systemcontaining static fluid. The device will hereinafter be termed either asurge eliminator or a surge dampening valve.

One of the objects of the present invention is to provide a surgeeliminator which may be connected in a hydraulic line and which will beoperative to decrease or eliminate the surge usually occurring whenfluid under high pressure is introduced into the fluid conductor, thedevice being designed to permit substantially unre stricted fluid flowthrough the line after the danger of the surge has been eliminated.

Another object of the invention is to provide a surge eliminator ordampening device which will operate in inverse proportion to thenecessity for such a device, in other words, if the pressure on fluidbeing introduced into a fluid conductor is high and one which wouldcreate a great surge in the fluid conductor, the device will beoperative to prevent such surge, opening slowly until the danger of thecreation of a surge is eliminated and then gradually accelerating in itsopening movement until unrestricted communication between the lineleading to the device and the line leading therefrom is established,conversely, if the pressure'introduced to the conductor is low andconsequently will cause a very slight surge, the valve will readily opento permit substantially unrestricted communication between the linesleading to and from the device.

A still further object of the invention is to provide a surgeeliminating device having a body with inlet and outlet ports and meanswithin the body to control communication between the inlet and outletports, such means being controlled in itself by fluid pressure dependentupon a contrast in pressure between the inlet and outlet of the device.

A further object of the invention is to provide,

a surge dampening valve having a body adapted for connection in ahydraulic line, the body containi'ng a port-controlling spool which isnormally disposed in communication-obstructing position and providing ahydraulic cushion for resisting the movement of the spool, means beingprovided to control the dissipation of the hydraulic cushion in responseto the force applied to the spool by the fluid. pressure introduced tothe valve.

Another object of the invention is to provide a surge dampening valvehaving a body with inlet and outlet ports and a spool for controllingcommunication between such ports, the spool being biased toward a closedposition and movable, in response to the introduction of fluid pressureto the inlet of the device toward an open position, the movement beingresisted by fluid to be displaced by the spool, the displacement of thefluid being controlled by valve means disposed in the device, the valvemeans being operated by a pressure drop caused by movement of the spoolin response to the application of fluid to the inlet of the device. Ifthe fluid pressure is high, the valve will tend to close and restrictthe escape of fluid being displaced by the movement of the valve spool,causing the spool to move more slowly. As the spool moves, it willgradually or progressively expose ports through which the fluid may passfrom the inlet to the outletv and the spool will continue to move untilsubstantially unrestricted. communication is established. As the portsare exposed, however, and the flow of fluid in the line leading from thedevice accelerates, the pressures at the inlet and outlet of the devicegradually become equalized reducing the danger of the creation of asurge and permitting the spool to move more rapidly.

A still further object of the invention is to provide a surge dampeningvalve which will be responsive to the pressure at the inlet and outletends thereof in such a manner that no changes or adjustments, other thanthose occurring automatically in the device itself, are necessary toobtain the optimum rate of opening under all conditions.

Another object of the invention is to provide a surge eliminating valveadapted for incorporation in a conductor of a hydraulic system toeliminate the usual surge of pressure when fluid under pressure issupplied to one end of the conductor, the valve being so constructedthat when fluid is supplied to the other end of the conductor orotherwise caused to flow in the opposite direction therethrough, it willoffer substantially no resistance to the movement of the fluid.

An object also, of the invention, is to so construct the surgeeliminator mentioned in the previous paragraphs that it will be smalland sure is introduced thereinto and then permit substantiallyunrestricted flow when the pressures at the inlet and outlet ends of thedevice are equalized, the mechanism further operating to quickly resetitself automatically for the next succeeding operation when fluid flowthrough the conductor is interrupted.

An object also is to provide a Surge eliminator of the type mentionedwhich will not require a tank or drain line to render its operationsuccessful.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred form of embodiment of the invention isclearly shown.

In the drawings:

Fig. 1 is a vertical longitudinal sectional view taken through a surgedampening valve formed in accordance with the present invention, thevalve shown being capable of permitting fluid flow in both directionstherethrough, the fiow in one direction only being regulated to dampenor prevent a surge.

Fig. 2 is a similar view of a modified form of valve in which flow in asingle direction only is permitted, this flow being regulated for thesame purpose.

Fig. 3 is a vertical traverse sectional view taken through the valveshown in Fig. 1, the plane of the section being indicated by the lineIII-III.

Fig. 4 is a longitudinal sectional view taken through a surge dampingvalve of the type shown in Fig. 1 showing the parts thereof in inactivepositions;

Fig. 5 is a similar view showing the parts in th positions occupiedimmediately following the introduction of fluid under pressure into thesurge damping valve;

Fig. 6 is also a similar view showing the parts in the positionsoccupied during reverse flow of liquid through the valve.

Referring more particularly to the drawings, numeral 2!) designates thefirst form of surge dampening device shown in the drawings. This device,as well as the second form of device, shown in Fig. 2 and which isindicated generally by the numeral 2|, includes a casing 22 formed oftwo pieces 23 and 24. The parts in valves 23 and 2| are substantiallyidentical and the same reference numerals will be used throughout,except, on the parts that are different. Parts 23 and 24 are providedwith threaded extremities 25 and 25-A to permit the connection of thedevice in a fluid conductor. Each extremity 25 and 25-A is formed with acentral bore, the bore 26 in part 23 being the inlet and the bore 21 inpart 24 being the outlet. Housing parts 23 and 24 are threadedlyconnected as at 28, a gasket 30 being disposed between these parts toprovide a fluid-tight joint. Body part 24 has a chamber 3| formedtherein, which is closed at one end by the body section 23. Both parts23 and 24 are recessed as at 32 and 33 to receive and locate a sleeveunit 34 which includes a tubular member 35 and a plug 36, the latterbeing formed from square stock, in this instance, and having aprojection 31 which is disposed in the tube 35 to close one end thereof.

Plug 36 has a flange which engages this end of the tube and is disposedin the recess 32 to locate the number 35. The flanged end of the plug istransversely slotted several times at right angles to provide openings38, which establish communication between the space in the chamber 3| atthe outside of the sleeve member 35 and the bore or outlet 21. Theprojection 31 seals the end of the tube 35 and cooperates therewith toprovide a closed end socket 39 the purpose of which will be hereinafterset forth. Near the opposite end of tube 35, the side wall thereof isprovided with longitudinally spaced sets of openings 43 which establishcommunication between the interior of the tube and the chamber 3| at theexterior thereof. The side wall of the tube is also provided withregistering slots 4| for receiving the end portions of a pin 42extending traversely through the sleeve; this pin also extendstraversely through a spool 43, which is disposed for sliding movement inthe sleeve. A coil spring 42-.A is arranged on the outside of the sleevebetween the flange on the plug 35 and the reduced ends of the pin 42,this coil spring tending to urge the pin and consequently the spooltoward the inlet end of the device. When the spool occupies its normalposition determined by the engagement of the pin with the ends of theslots 4|, the skirt of the spool covers the openings 40 and preventscommunication between the inlet and outlet of the device.

The spool 43 has a central web or wall 44 in which is formed an orifice45; a needle valve 46 cooperates with the wall of this orifice tocontrol fluid fiow to and from the socket 353 through the orifice. Theneedle valve 48 is formed on a member 41 having a disk portion 48 whichis slidable in the socket 39 provided in the sleeve 35 between the spool43 and the plug 31. The member 41 has a body portion in which a slot 50is provided, this slot receiving a transversely extending pin 5|, theend portions of which are disposed in registering openings formed in thewall of spool 43. A coil spring 41-A disposed between the web 44 of thespool and the end of the body portion of the member 41, normally tendsto separate the spool and the member 41 so that the needle valve 46 willbe held spaced from the seat formed by the walls of the orifice 45 inthe web 44. The spacing of the needle valve and seat is limited by thepin 5|. The disk portion of the member 41 has an orifice 52 formedtherein, which orifice provides the only communication between thesocket 35, at one side of the disk 48 and the space 52A between themember 41 and the spool 43; the latter space 52A communicates with thechamber 3| through the orifice 45, the interior of the spool 43 andregistering openings 53 formed in the spool 43 and sleeve 35.

In the form of the invention shown in Fig. 2, the spool 43-A has a solidforward end through which a transverse bore 53-A is formed; this bore53-A registers with the openings 53 in the sleeve 35 and with themestablishes communication between the orifice 45-A and chamber 3|. Thespool 43-A is the only part in the form of the invention shown in Fig. 2which is different from the corresponding parts in the form shown inFig. 1, although two other parts, about to be described, are containedin the latter form and are omitted from the form shown in Fig. 2. Theseparts are a poppet valve 54 and a, coil spring 55, which is employed tourge the poppet valve into seated engagement with the spool 43. Thepoppet valve 54 is reduced in diameter as at 54-A and has a plurality ofopenings 56, extending angularly therethrough, these openings permittingfluid to fiow through the poppet valve at the reduced portion thereof,in the operation of the device. Valve 54 is disposed for slidingmovement in the body section 23 and is chamfered as at 51 for engagementwith the end of the valve spool 43, this member having a v seat providedthereon. When the poppet valve 54: and spool:- 43 are in engagement, achamber 58 is; formed in the valve spool between the end of the poppetvalve 54 and the web 44.

This chamber 58 connects orifice 45 with openings 53, and is in constantcommunication with the chamber section 31, the latter being, in turn, incommunication with the outlet. 21. With this arrangement, the pressureexisting in the outlet 21- also exists inchamber section 31, ports 53,chamber 58, opening 45 and in the space 52A between the web 44 and themember 41, when the needle valve 46 is open. Under normal operatingconditions, spring 55 maintainspoppet valve 54 seated against the spool43 and permits no flow from the inlet 26 to the chamber 58. This: poppet-4 constitutes a check valve, however, to permit.

reverse flow through the device when pressure in the outlet end exceedsthat in the inlet end. When flow in this direction takes place, as shownby arrows in Fig. 6, the fluid enters the device through the outlet port21, flows through the grooves 38 in the plug 36 to the chamber section3i, then through the ports 53 to the chamber 58. The pressure of thisfluid moves valve 54 to an open position in opposition to the spring 55and the fluid flows between the poppet valve 54 and the end of the spool43 to the ports 55, these ports communicating with the inlet 26 throughwhich the fluid leaves the body during reverse flow therethrough.

In the modified form of the invention shown in Fig. 2, the poppet valve54 and its spring 55 are omitted, the spool valve 43-A also having thechamber 58 omitted therefrom. This modification does not provide for orpermit reverse flow through the device. Its use is, therefore, limitedto a portion of a hydraulic system, in which fluid flows in onedirection only but the surge dampening functions are the same in bothforms of the invention.

When either of these devices is utilized it is placed in a conductorconnected with a source of fluid pressure. This fluid pressure flowsinto the device through the inlet 25, its force being applied throughthe check valve 54 to the forward end of the spool valve 43 or 43-A. Theforce of this fluid tends to and does move the spool valve toward theoutlet or to the right as viewed in Fig. 5 of the drawings, to expose oropen the ports 40. Movement in this direction by the spool 43 or 43-Awill start to displace fluid as indicated by the arrows in Fig. 5 fromthe socket 39 formed by the inner end portion of the tube or sleeve 35.The fluid being displaced must flow through the orifices 52 and 45 tothe chamber 58 and out through openings 53. Since the orifice 52 isrelatively small, it will resist the flow of fluid from the socket 39causing the pressure in such socket 39- to increase. A pressuredropbetween the inner and outer ends of the orifice 52 will thus be created,the higher pressure bein at the inner side of the disk 48. This higherpressure will tend to resist movement of the disk 41 and needle valve46. Further movement of the spool 43 while movement of the disk 4! isresisted causes the seat formed by the' sides of the orifice 45 toapproach the needle valve thus tending to close the orifice. Thisclosing'tendency will reduce the flow of fluid from the socket 39 andsince fluid will thus be confined therein, it will yieldably resistinward movement of the spool 43. Since the movement of spool 43 isresisted, the number of holes immediately exposed will be limited and,

6 therefore, the volume of fluid flowing through the device 20 islikewise. limited. This flow-limiting characteristic is temporary,however,,since the disk 41 is spring-pressed toward the inner end ofsocket 39 and the orifice 52 is continually open, some fluid will flowfrom socket 39 to space 52'A allowing thedisk to move in response totheforce of sprin 4'l-A into thesocket 39 which. movement will permitneedle valve 46 to move somewhat gradually away from the walls oftheorifice. 45. When this orifice is even slightly open, some fluid willflow therethrough permitting the spool 43 to move further into thesocket. As the spool 43 moves into the socket; more of the ports 45:will be-progressively exposed to establish additional communication andpermit a greater volume of. fluid flow between the inlet 26 and theoutlet 21. The rates at which the spooland the disk are permitted tomove will be controlled, however, by the difference in pressure betweenthe inlet and outlet end, so that the degree of communicationestablished between the inlet and outlet of the device will increase ininverse pro-- portion. to the pressure of. the fluid entering the inlet26. If this pressure is high and tends to move the spool valve 43suddently, the needle valve 46, will move further toward a completelyclosed position and movement of the spool will be retarded- As mentionedabove, however, some fluid will flow through the; orifice 52 allowingthe needle valve to move away from the orifice 4'5 and the flow of fluidfrom behind the spool 43; the spool will be permitted to move inwardlyin the socket 39 gradually. In the device, as constructed', the rate ofmovement of spool .43 depends upon four conditions three of which arefixed, one fixed condition, is the area of the disk 48, another is thearea of orifice 52, another is the force of spring 4l-A. The fourth andvariable condition is the differential in pressure between the inlet andoutlet ends of the device. As long as the pressure drop through theorifice 52 remains unchanged spring ll-A, will balance the forcetending. to close needle valve 46 and the flow past the valve will beuniform causing uniform. movement of spool 43. It is important to theoperation of the device that the leakage. from socket 39 be parallel tothe flow through the orifice 45 so that it will not afiect suchoperation. As long as the total of the leakage and the flow throughorifice 45 is insufiicient to afiect the pressure differential throughorifice 52, the leakage will be unimportant. It will be observed that asthe ports 40 are exposed, fluid will flow directly from the inlet to theoutlet permitting the pressures in these two regions to approachequalization. As the inlet port pressure and the outlet port pressureapproach equalization, the spool will move further to the rig-htexposing additional ports and providing for full flow through thedevice.

As shown in both forms of the invention, the spring 4'l-A is arrangedbetween and supported by the spool 43 and part 41; the latter will offerresistance to the flow of fluid through the device only while the spool43 is moving toward an open position or when there is a differential inpressure between the inlet and outlet end of the cas ing. As soon as theinlet and outlet pressures are equalized, spring 4'l-A has no effect onthe flow and the only resistance thereto will be offered by the spool 43under the influence of sprin 42-A. Thespring 42-A, however, isrelatively weak and will, therefore, offer a minimum of resistance tothe flow of fluid through the device. It will be observed from thedrawing that several sets of openings 40 are provided, these beingspaced longitudinally of the device to be progressively exposed as thespool 43 moves into the socket formed by the sleeve-like partition 35.

One feature of the invention is that the valve formed in accordancetherewith provides for a gradually accelerated flow from the inlet tothe outlet. This flow will be substantially unrestricted after thenecessity for the dampening effect is reduced and will remainunrestricted as long as fluid continues to flow through the valve. Assoon, however, as flow is interrupted, the valve will be quickly resetto its orig al p t o ready to prevent a surge when fluid flow throughthe conductor is again initiated. As the valve is constructed, it willbe responsive to the pressures in the inlet and outlet ends in such away that no changes or adjustments are necessary to obtain the optimumrate of opening under all conditions. It has been pointed out that therate of openin of the valve will be slower if high pressure is appliedto the inlet than if a low pressure is applied thereto. This feature ofoperation is due to the hydraulic unbalance of the needle valve and itsSupporting member. When pressure is applied to the inlet of the device,this pressure will be eifective over the end of the valve spool 43. Theforce of this pressure will tend to move the valve spool into the socketprovided by the sleeve-like partition 35 and the pressure in this socketwill build up to equal the pressure in the inlet. This pressure iseffective over the entire inner area of the disk 48 and is substantiallybalanced on the opposite side of the disk, except for the portion of theneedle valve which is exposed to the area of the orifice 45; this areais exposed to the pressure existing in chamber 58, which issubstantially equal to the outlet port pressure. There will thus be aforce applied to the disk which tends to close the needle valve 46. Ifthis force is less than the force exerted by the spring 4l-A, the needlevalve will remain open permitting some fluid to flow through the orifice45; the spring 41-A has been so calculated that it will exert a forcegreater than the force tendin to close the valve under all normaloperating conditions. Since there will, therefore, always be some flowpossible through the orifice 45, spool 43 will be capable of commencingto move toward an open position when fluid pressure is applied to theinlet. When the fluid pressure is high, however, the effective force ofspring 41-A will be less than when the inlet port pressure is lower andneedle valve will move closer to a closed position to further restrictflow through orifice 45. The volume of fluid flow through orifice 45will, therefore, depend upon the difference between inlet and outletport pressure; if this pressure difference is slight the volume of fluidflowing through the port will be greater permitting the spool 43 to moveat a faster rate. It will thus be seen that the rate of opening of thevalve will be in inverse order to that of the pressure differentialexisting between the inlet and outlet ports.

While the form of embodiment of the present invention as hereindisclosed constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What is claimed is:

1. A surge dampening device comprising a body with an internal chamberand inlet and outlet ports communicating therewith; a valve elementdisposed for movement in said chamber to control communication betweensaid inlet and outlet ports; means yieldably urging said valve elementtoward a position in which communication between said inlet and outletports is prevented, a higher pressure in said inlet port than in saidoutlet port tending to move said valve element in opposition to saidurging means to a position providing for communication between saidinlet and outlet ports; a second means for controlling the movement ofsaid valve element toward open position, said second means having asecond fluidreceiving chamber disposed to have fluid displaced therefromby movement of said valve toward open position; means forming a normallyopen passage between said second fluid-receiving chamber and saidoutlet; a valve seat in said passage; and a valve normally spaced fromsaid seat and disposed for movement toward the same to close saidpassage in response to a higher fluid pressure in said second chamberthan in said outlet.

2. A surge dampening device comprising a body with an internal chamberand inlet and outlet ports communicating therewith; a spool valvedisposed for movement in said chamber to control communication betweensaid inlet and outlet ports; means yieldably urging said spool toward aposition in which communication between said inlet and outlet ports isprevented, a higher pressure in said inlet port than in said outlet portserving to move said spool in opposition to said urging means to aposition providing for communication between said inlet and outletports; means for regulating the rate of movement of said spool towardopen position having a second chamber to which inlet port pressure istransmitted; a passage leading from said second chamber to said outlet;means in said passage forming a valve seat; a metering valve disposedfor movement toward and away from said seat to control fluid flow fromsaid second chamber; and a piston element in said second chamber foractuating said metering valve, said piston element forming an orifice insaid passage to create a pressure differential on opposite sides of saidpiston and impart movement thereto.

3. A surge dampening device comprising a body with an internal chamberand inlet and outlet ports communicating therewith; a spool valvedisposed for movement in said chamber to control communication betweensaid inlet and outlet ports; means yieldably urging said spool toward aposition in which communication between said inlet and outlet ports isprevented, a higher pressure in said inlet port than in said outlet portserving to move said spool in opposition to said urging means to aposition providing for communication between said inlet and outletports; means for regulating the rate of movement of said spool towardopen position having a second chamber to which inlet port pressure istransmitted by said spool; a passage leading from said second chamber tosaid outlet, said passage having a valve seat formed therein; valvemeans supported for movement toward and away from said valve seatindependently of said spool to control fluid flow through said passage;spring means tending to urge said valve means toward an open position,and means responsive to a greater pressure in said second chamber thanin said outlet to move said valve means toward said seat in oppositionto said sprin means.

4. A surge dampening device comprising a body with an internal chamberand inlet and outlet ports communicating therewith; a spool valvedisposed for movement in said chamber to control communication'betw'eensaid inlet and outlet ports; means yieldably urging said spooltoward aposition in which communication between said inlet and outlet ports isprevented, a higher pressure in said inlet port than in said outlet portserving to move said spool in opposition to said urging means to aposition providing for communication between said inlet and outletports; means for re ulatin the rate of movement of said spool towardopen position having a fluidreceiving socket at one end of said spool;an orifice in said spool communicating with said outlet, movement ofsaid spool toward an open position serving to exhaust fluid from saidsocket through said orifice; a disk having a second orifice disposed formoved ent in said socket; a needle valve supported by said disk adjacentthe orifice in said spool; and resili nt me: 11s tending to move saiddisk to withdraw said needle valve from said orifice.

5. A surge dampening device comprising a body with an internal chamberand inlet and outlet ports communicating therewith; a ported sleevedividing said chamber into inlet and outlet sections; a spool disposedfor movement in said sleeve to control communication between saidsections; means yieldably urging said spool toward a position preventingcommunication between said sections, said spoolmoving in opposition tosaid urging means in response to the introduction of fluid pressure tosaid inlet; and means for regulating the rate of movement of said spoolhaving a fluid-containing chamber; a movable partition having an orificedividing said chamber into inner and intermediate pressure zones, thelatter being between said spool and partition; a wall in said spoolhaving a .port to connect said intermediate pressure zone with saidoutlet chamber section; and a normally open needle valve carried by saidpartition to control fluid fiow through the port in said wall.

5. A surge dampening valve comprising a body with an internal chamberand inlet and outlet ports; a sleeve-like partition dividing saidchamber into inlet and outlet sections communicating with said inlet andoutlet ports respectively, said partition having ports establishingcommunication between said sections, said sleeve-like partitionproviding a socket communicating with the outlet section of saidchamber; a spool member disposed for movement in said socket to governfluidflow through the ports in said sleeve; means tending to urge saidspool outwardly of said socket, said spool. being moved inwardly in saidsocket and displacing fluid therefrom in response to a difierentialbetween inlet and outlet port pressure; and means for controlling thedisplace ment of fluid from said socket by the movement of the spoolthereinto, said means having a needle valve pressure differentialcreating means for actuating said needle valve.

'7. A surge eliminator comprising a body with an internal chamber andinlet and outlet ports; a sleeve-like partition dividing said chamberinto inlet and outlet sections communicating with said inlet and outletports respectively, said partition having ports establishingcommunication between said sections, said sleeve-like partitionproviding a socket communicating with the outlet section of saidchamber; a spool member disposed lor movement in said socket to governfluid flow through the ports in said sleeve; spring means yieldablyurging said spool outwardly of said socket, said spool beingmoved'inwardly in said socket and displacing fluid therefrom in responseto inlet port pressure; 'means for controlling the displacement of fluidfrom said socket by the movement of the spool thereinto, said meanshaving a needle valve; means tending to urge said needle valve toward anopen position; and a disk with an orifice between said spool and theinner end of said socket, said disk and said needle valve beingconnected for movement in unison.

8. A surge eliminator comprising a body having aligned inlet and outletports and an internal chamber; a sleeve-like partition dividing saidchamber into inlet and outlet sections cormnunic'ating with said inletand outlet ports respectively, said inlet section being closed atone endand communicating with said outlet section through spaced ports providedin said partition; a spool member disposed for movement in said inletsection to control fluid flow through said spaced ports, said spool andpartition providing a passage with an orifice establishing communicationbetween the closed end of said section and said outlet section; meansresiliently urging said spool toward a position to close the ports insaid partition, said spool being exposed and responsive to inlet portpressure to move in opposition to said resilient urging means to opensaidp'orts; means responsive to the difierence in inlet and outlet portpressures for controlling the flow of fluid through the passage providedby said spool and partition, said means having a needle valve forcooperation with said orifice; and a disk movably supporting said needlevalve, said disk being disposed in the closed end of said inlet sectionbetween the spool and the inner end, the opposite sides of said diskhaving area's exposed to unequal pressures when differences betweeninlet and outlet port pressures exist, such unequal pressures serving tohydrostatically unbalance said disk.

9. A surge eliminator comprising a body having an internal chamber andinlet and outlet ports communicating therewith at opposite ends of thebody; a tubular partition dividing said chamber into inlet and outletsections communicating with said inlet and outlet ports respectively,said tubular partition being closed at the end remote from said inletport; spaced ports in said partition adjacent the end proximate to saidinlet port, said spaced ports establishing communication between saidinlet and outlet cham ber sections; a spool member disposed for slidingmovement in said tubular partition; spring means normally urging saidspool member into a position to block the spaced ports in saidpartition, one end of said spool member being exposed to inlet portpressure and the other end being spaced from'the closed end of saidtubular partition to provide a pressure chamber; a passage formed insaid spool and partition to connect said pressure chamber and saidoutlet section; an orifice in said passage; a needle valve; a disk-likepiston disposed for movement in said tubular partition between theclosed end thereof and said spool member, said piston supporting saidneedle valve for movement toward and away from said orifice, said pistonhaving a second orifice; and spring means between said spool member andpiston, said last-named spring tending to move said needle valve awayfrom said first-mentioned orifice.

10. A surge dampening valve comprising a body with inlet and outletports; a normally closed valve in said body for controllingcommunication between said ports, said valve being movable toward openposition by the application of fluid pressure to said inlet port; afluid containing chamber in said body, movement of said valve towardopen position displacing fluid from said chamber; flow control means forgoverning the displacement of fluid from said chamber, said means havinga flow restrictor to create a pressure drop on the fluid flowing fromsaid chamber; and a second valve movable relative to the first mentionedvalve and responsive to such pressure drop to restrict fluid flow fromsaid chamber.

11. A surge dampening valve comprising a body with inlet and outletports; a normally closed valve in said body for controllingcommunication between said ports, said valve being movable toward openposition by the application of fluid pressure to said inlet port; afluid containing chamber in said body, movement of said valve towardopen position displacing fluid from said chamber; a passage between saidchamber and one of said ports; flow control means in said passage, saidflow control means having flow restricting means to cause a pressuredifferential on fluid flowing from said chamber through said passage;and a second valve movable relative to said normally closed valve andresponsive to such pressure difierential to restrict the flow of fluidthrough said passage.

12. A surge dampening device comprising a body with inlet and outletports; a normally closed valve in said body for controllingcommunication between said ports, said valve being movable toward openposition by the application of fluid pressure to said inlet port; meansfor controlling the rate of opening movement of said valve, said meanshaving a fluid-receiving chamber; a single restricted outlet leadingfrom said chamber, movement of said valve toward an open positiontending to increase the pressure on the fluid contained in said chamber;and a valve element disposed for movement in said chamber independentlyof said first-mentioned valve and responsive to the pressure of thefluid in said chamber to reduce the size of said restricted outlet.

13. Surge dampening means comprising a body with an internal chamber andinlet and outlet ports communicating therewith; a spool valve disposedfor movement in said chamber to control communication between said inletand outlet ports; means yieldably urging said spool toward a position inwhich communication between said inlet and outlet ports is prevented, ahigher pressure in said inlet port than in said outlet port serving tomove said spool in opposition to said urging means to a positionproviding for communication between said inlet and outlet ports; meansfor regulating the rate of movement of said spool having a passagewithin said body through which fluid is forced by the movement of saidspool valve toward open position; a valve seat in said passage; a secondvalve movable relative to said spool valve and cooperating with saidseat to control fluid flow through said passage; means for actuatingsaid second valve having a piston and a restricted orifice forming partof said passage and establishing communication between opposite sides ofsaid piston, the latter being responsive to an excess in pressure on theside thereof remote from said seat caused by fluid flow through saidorifice to move said valve toward a closed position; and yieldable meansfor urging said valve actuating means toward a valve opening position,the approach toward an equalization of pressure in said inlet and outletserving to permit opening movement of said second valve.

14. A surge dampening valve comprising a body with inlet and outletports; a normally closed valve in said body for controllingcommunication between said ports, said valve being movable toward openposition by the application of fluid pressure to said inlet port; flowcontrol means for governing the rate of movement of said valve towardopen position, said flow control means having a chamber and a singlerestricted passage leading therefrom, movement of said normally closedvalve toward open position causing fluid flow from said chamber throughsaid restricted passage to create a pressure differential in saidpassage; and a second valve in said passage movable relative to saidnormally closed valve, said second valve being responsive to suchpressure differential to restrict the flow of fluid from said chamberconcurring with and dependent upon movement of said normally closedvalve toward open position.

15. A surge dampening valve comprising a body with inlet and outletports; a normally closed valve in said body for controllingcommunication between said ports, said valve being movable toward openposition by the application of fluid pressure to said inlet port; meansfor controlling the rate of opening movement of said valve, said meanshaving a fluid containing chamber; a wall member disposed for slidingmovement in said chamber, movement of said normally closed valve towardopen position tending to move said wall member and increase the fluidpressure in a part of said chamber; a single outlet leading from saidchamber, said outlet being restricted; and a second valve movableindependently of said normally closed valve and cooperating with saidrestricted outlet to control fluid flow from said chamber, said secondvalve being actuated by said wall member in response to fluid pressurein said part of said chamber to reduce the effective size of saidrestricted outlet.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 956,789 Allan May 3, 1910 1,258,167 Vollmann Mar. 5, 19181,379,092 Fraccascia et al. May 24, 1921 1,583,834 Humphrey May 11, 19261,891,977 Gould Dec. 27, 1932 2,161,642 Stroup June 6, 1939 2,289,946Weatherhead July 14, 1942 2,339,101 Parker Jan. 11, 1944 2,404,924Sacchini July 30, 1946 2,538,383 Sandwell Jan. 16, 1951 2,554,390Stevenson May 22, 1951 2,555,334 Green June 5, 1951

